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MySQL 如何查询重复次数大于 N 的数据的个数？
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5 个回答
最简单直观的就是
select name, count(name) as c from table_name group by name having c > N;
在name上面做索引
explain一下大概就是
+----+-------------+-------+-------+---------------+----------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+----------+---------+------+------+-------------+
| 1 | SIMPLE | test | index | NULL | id_index | 4 | NULL | 9 | Using index |
